Firefighting foam concentrates are mixtures of foaming agents, solvents and other additives. These concentrates are intended to be mixed with water, the resulting solution foamed by mechanical means, and the foam projected onto the surface of a burning liquid. A particular class of firefighting foam concentrates is known as an aqueous film-forming foam (AFFF). AFFF concentrates have the quality of being able to spread an aqueous film on the surface of hydrocarbon liquids, enhancing the speed of extinguishment of fuel and solvent fires. Surfactants added to AFFF lower surface tension values which permits the foam to spread on the surface of the hydrocarbon liquids.
Aqueous film-forming foams provide a blanket to cover the fuel surface excluding air preventing further ignition of the fuel. For this reason aqueous film-forming foam compositions are particularly desirable for extinguishing fires involving flammable fuels, such as gasoline, naphtha, diesel oils, hydraulic fluids and other hydrocarbons.
Aqueous film-forming foams typically include a surfactant to impart important film forming properties that are useful in the extinguishment of burning liquids. Commonly used anionic hydrocarbon surfactants include alkyl ether sulfates and alpha olefin sulfates. What is needed are fluorinated sulfate surfactants which can enhance the fire extinguishment properties and stability of firefighting foams, including reducing surface tension and improving foam expansion.